1. Field of the Invention
This invention relates to control of a dump-valve of turbocompressors.
2. Description of the Prior Art
It is known that heat engines supplied by turbocompressors always include a dump-valve bypassing the turbine side of the turbo-compressor so that the supply pressure to the engine will not increase indefinitely to a dangerous level.
To control this dump-valve, it is known to use a pneumatic actuator having a diaphragm, with a return spring acting to close the valve, and to cause the pressure collected at the outlet of the compressor portion to open the actuator, either upstream or downstream the butterfly valve, or at the level of the engine exhaust, above the turbine. This device has the advantage of being simple and prevents the intake pressure from reaching a point which will be harmful to the engine.
However, it is known that a turbocompressed engine can, under transitory conditions, tolerate supercharging much greater than that allowed under stabilized conditions. This is explained more particularly by the fact that the temperature of the surfaces in contact with the gasses in the engine is a priori lower at the beginning of acceleration than under equivalent stabilized conditions, and also by the improved cooling capacity of the heat exchanger. Other factors such as enrichment during acceleration, help to allow a temporary increase in the supercharging pressure limit. Therefore, it would be preferable in the simple device mentioned above to delay the moment at which the dump-valve comes into play during acceleration periods.